This invention concerns an extruding equipment with multi-tubes which can be used for extrusion of fluid plastic materials to make various formed products or for coating of fluid chemicals onto the web surface.
The typical conventional extrusion dies used for making plastic films among many types are as follows:
Coat hanger type (normally called as xe2x80x9cT-Diexe2x80x9d) which is explained in details hereinafter
Manifold type of which die is equipped with holding chambers (called as xe2x80x9cManifoldxe2x80x9d)
Same as above Manifold type but with a built-in agitating roll inside each manifold. This agitating roll prevents deterioration of the fluid materials.
Hereinafter, the outline of the T-Die of Coat hanger type is described with reference to Drawing 24. The illustration (A) in the drawing shows the section when viewing from the front and (B) shows the Uxe2x80x94U section of the illustration (A). This extrusion die 200 has such a T-shape construction die 201 as shown in the illustration (A). The plastic material melted by the heater in the preceding fluid supply equipment (not shown) is sent to the die via the pipe 202 and coupling 203 by a gear-pump or an extruder (not shown). As shown in the illustration (A), the fluid plastic material flows and spreads from the center of the die 201 in the cross machine direction along the internal wall, then goes through the slit 204 to the slice lips where the material is extruded out into a film of a pre-determined width.
On the other hand, a so called xe2x80x9cco-extrusionxe2x80x9d product is sometime produced by this Coat hanger type extrusion die. The xe2x80x9cco-extrusionxe2x80x9d is such a process where more than two different plastic materials are extruded from the die to form, by lamination, certain layers of a multi-layer product. The extrusion die for production of this kind of product is basically similar to 201 die. What is different is the so-called xe2x80x9cfeed blocksxe2x80x9d mounted just before the extrusion die 201. At this xe2x80x9cfeed blocksxe2x80x9d, some pre-adjustment of the melted plastic material can be made before going to the extrusion die, for purpose of getting a more uniform thickness for each layer of the product. Of course, it is very important to keep a stable uniform flow of stock for all of the layers.
Basic problems in the flow of raw materials before or inside the extrusion die have not yet been solved while various improvements of the die itself for extrusion of one or more different plastic materials have been made. It is hard to produce uniform extruded products by such an extrusion die as shown in Drawing 24 because the amount of raw material extruded from the outlet of the die per hour in the cross machine direction could vary from location to location due to the difference in the velocity of raw materials flow inside the die, for example, the velocity in the flow line xe2x80x9caxe2x80x9d and that of the flow line xe2x80x9cbxe2x80x9d are different. Another problem is some deterioration of quality of the products caused by the shearing force to the fluid raw materials and different retention time of the raw materials in the die due to the difference in the velocity among the locations. In addition, the relatively large internal volume of such die requires a bigger volume and more time in refilling of the raw materials at each strat-up time, which results in a bigger loss of such raw material. More time and detergent for washing is required, too, because of the large internal volume.
As the die of this design has such a slit portion as shown in (B) of Drawing 24, some deformation of the slit portion takes place by so called xe2x80x9cClam-shell phenomenons (the die lips being opened)xe2x80x9d. Such deformation is variable from time to time by the change in the fluid viscosity and the fluid volume extruded. A sophisticated automatic control system to adjust the lips opening is available for installation so that a balanced flow of the fluid raw material in the die could be secured for producing an uniform layer. However, the high cost of such a control system is another problem. On top of the above mentioned problems, this die has another problem, that is, the change of the coating width takes time and is not so easily done.
As for the co-extrusion type, unsolved problems due to multi-layers structure still remain even though a lot of improvements of the die itself have been made by many people. The major reasons for this problem are the unstable flow of the fluid raw materials among layers and the cross machine direction profile of thickness of each layer could be easily deteriorated. The cause for unstable flows among layers is the large influence of the shearing force at the contacting surface between two layers which is called as xe2x80x9cWelded linexe2x80x9d where the lamination of the two layers is very poor because of less dispersion of high molecule chains. The instability among layers results in the uneven wave and reduces the value of the product. The cross machine direction thickness profile of each layer easily gets uneven and causes a so-called xe2x80x9cwrapping phenomenonxe2x80x9d, that is, the higher viscosity fluid is wrapped by the lower viscosity fluid. Such a technology to make a pre-adjustment of melted plastic materials in order to avoid the above mentioned xe2x80x9cwrapping phenomenonxe2x80x9d has been developed but it is not enough to completely stop the wrapping phenomenon. The method of the pre-adjustment must be also developed for each specific features of the phenomenon respectively and is not practical for use in the industry.
The first object of the invention is to make an extruding equipment available to the industry of which manufacturing cost is low and capable to reduce the raw material and time required for the initial filling at the time of start-up and to reduce the loss of the raw material, too. The second object of the invention is to make an extruding equipment available to the industry which is capable to produce products of uniform and good quality. The third object of the invention is to make an extruding equipment available to the industry which is capable to produce the film with almost nil variation of thickness in the cross machine direction. The fourth object of the invention is to make an extruding equipment available to the machinery manufacturers which allows more tolerance for machining and requires less skill in manufacturing.
In order to achieve the above mentioned objects, this Multi-tube extruding equipment of which patent is claimed under the first claim hereinafter comprises
a joint to connect the bunched tubes and the material supply equipment by a hose etc.
multi-tubes of which one ends at the material inlet side are bunched and securely inserted into the joint, and the other ends at the material outlet side are lined up in a plane in the cross machine direction.
The secure fastening of the other ends of the lined up tubes in a plane means not only the fastening of the ends of the whole tubes lined up in a plane and in the cross machine direction to the extrusion die but also the fastening of the ends of each divisional bunch of tubes also lined up in a plane and in the cross machine direction,bunch by bunch, to the extrusion die. The unfastened ends of the tubes could be used in some applications.
The advantages of an extruding or coating equipment having such components as mentioned hereinabove are as follows:
1) the manufacturing cost is cheaper than that of conventional equipment which is fabricated from the casted or forged metal block and finished by fine machining
2) less amount of the material and time for the initial filling and a minimized loss of the material at the time of start-up due to its smaller internal volume (total of the internal volume of the tubes) than such conventional extruding die as 101 of Drawing 24
3) less consumption of the detergent and time for washing of the equipment due to the same reason as that of above 2)
4) quicker work in case of a change of the product.
As the above mentioned tubes are used on this equipment it is possible to have the direction of the material inflow and the direction of the outflow at right angles to each other. In other words, both ends of the tubesxe2x80x94one ends on the material inlet side and the other ends on the material outlet sidexe2x80x94could be installed at right angles to each other. This kind of arrangement is impossible on the conventional extruding equipment or coating equipment. The installation angles of the direction of the material inflow and that of the material outflow could be not only the right angles but also any other angles.
This Multi-tube extruding equipment is capable to handle such various materials as
hot melt plastic material, for example, high-molecule chemical compound
melted metal
fluid coating material, paint etc.
solid materials like powder, granule
gaseous materials.
As for the raw material distribution tubes, the material, the shape (especially, square or round section), the diameter and length, and the quantity of tubes are variable depending upon the extruding material or coating material and also the application. A careful design and engineering should select such parameters, especially the quantity after due consideration to the hydraulic pressure of the fluid material flowing inside the tube and the width of extruding or coating.
This Multi-tube extruding equipment under the second claim hereinafter with a certain number of material distribution tubes of an identical length enables an uniform delivery of the material from each tube as the supply amount per hour from every tube is maintained same. In other words, the variation of the supply volume of the material in the cross machine direction is regarded xe2x80x9cnilxe2x80x9d. The constant and uniform material flow in each tube also makes possible to have an excellent supply of the material for an excellent extrusion. On the contrary, the different retention time of the raw material in the die of the conventional extruding equipment causes some deterioration of the quality of the finished product.
This Multi-tube extruding equipment under the third and fourth claims hereinafter with the coating die is ideal for film coating of chemicals or paints on the surface of the base material. The equipment under the third claim hereinafter has the die lips where the other ends of the tubes are securely fastened to and also has the slit to convert the raw material into the film of a pre-determined thickness before extruding out through the die lips. The film thickness can be adjustable within the range from 0.01 xcexcm to a few mm and the thickness variation across the machine direction can be maintained to the level of xe2x80x9cnearly zeroxe2x80x9d.
The equipment under the fourth claim hereinafter has a flow rectifying attachment inside the slit on the outlet side of the tubes. This arrangement enables to make the slit larger and the fabrication work easier because a bigger machining tolerance is allowed (for example, the tolerance of the slit at 0.3 mmxc2x13xcexc per 1 meter width can be replaced by a more generous tolerance of 3 mmxc2x130xcexc). The larger slit also enables this equipment to handle fluid materials of higher viscosity. The equipment under the third and fourth claims hereinafter, of course, can be used for extrusion-lamination, too.
The following effects are brought by the invention of the Multi-tube extruding equipment:
Very low manufacturing cost of the equipment
Almost no time and no raw materials required for the initial filling of the equipment at the time of start-up
Minimized loss of the raw materials
Stable production of goods of high and uniform quality
Nearly zero variation of thickness across the machine direction
Larger tolerances for machining and less professional machining skill